Chain for grate conveyor or the like

ABSTRACT

A two-piece chain link assembly and a chain for a grate conveyor or the like formed by a plurality of such two-piece chain link assemblies connected together. Each two-piece chain link assembly comprises a &#39;&#39;&#39;&#39;chain link proper&#39;&#39;&#39;&#39; which includes a yoke at one end and a neck at the opposite end, the neck of one &#39;&#39;&#39;&#39;chain link proper&#39;&#39;&#39;&#39; being received by and pivotally connected to the yoke of a contiguous chain link proper. A nonintegral separate cover member having gas passage slots or apertures therein is provided in overlying relation to each chain link proper, each cover member including at one end thereof projecting lips which are pivotally connected to a pivotal support moving with the conveyor such as a pipe spacer lying on the same transverse axis of the grate conveyor as the pivotal axis of the connection between the corresponding chain link proper and a contiguous chain link proper. The other end of each cover member includes a tail portion having a part thereof which underlies an end of the cover member of a continguous chain link assembly.

United States Patent [191 Hartwig CHAIN FOR GRATE CONVEYOR OR THE LIKE [75] Inventor: Walter J. Hartwlg, Oconomowoc,

Wis.

[73] Assignee: Allis Chalmers Corporation, Milwaukee, Wis.

[22] Filed: Sept. 1, 1971 [21] Appl. No.: 176,850

[52] US. Cl. ..l98/l95, 198/189 Primary Examiner--Richard E. Aegerter Assistant Examiner-Joseph E. Valenza Attorney Robert C. Sullivan, Arthur M. Streich and Robert B. Benson [5 7] ABSTRACT A two-piece chain link assembly and a chain for a grate conveyor or the like formed by a plurality of such two-piece chain link assemblies connected together. Each two-piece chain link assembly comprises a chain link proper which includes a yoke at one end and a neck at the opposite end, the neck of one chain link proper being received by and pivotally connected to the yoke of a contiguous chain link proper. A nonintegral separate cover member having gas passage slots or apertures therein is provided in overlying relation to each chain link proper, each cover member including at one end thereof projecting lips which are pivotally connected to a pivotal support moving with the conveyor such as a pipe spacer lying on the same transverse axis of the grate conveyor as the pivotal axis of the connection between the corresponding chain link proper and a contiguous chain link proper. The other end of each cover member includes a tail portion having a part thereof which underlies an end of the cover member of a continguous chain link assembly.

8 Claims, 11 Drawing Figures CHAIN FOR GRATE CONVEYOR OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved chain construction for use as a grate chain on a grate conveyor or the like.

The invention will be described as embodied in a traveling grate conveyor associated with a Grate-Kiln system in which the traveling grate carries load material such as pelletized ore or the like through a drying zone or zones and a preheating zone or zones before discharging the load material into a rotary kiln. The load material carried by the conveyor may be at a temperature in the range of from 600F. to 2l0OF., for example, depending upon the zone in which the temperature is measured and also depending on the location at which the temperature reading is taken depthwise of the bed of material on the grate conveyor.

2. Prior Art Compared to Present Invention In the prior art relating to grate conveyors for use with Grate-Kiln systems or the like, the pivotally connected links of the conveyor chains to which the grate members are connected are conventionally made of one-piece metal castings, including a pair of laterally spaced chain bar sides formed at one of their ends to define a yoke portion, the chain bar sides merging at their opposite ends to define a neck portion, the prior art chain link also including an integrally cast thin wall arched cover. The structure just described is one link in the prior art chain, and it will be understood that a plurality of such links are pivotally connected to each other with the neck portion of one chain link being received within the yoke portion of the next succeeding contiguous chain link. The plurality of pivotally connected chain links are known in the art as a chain strand. The term chain link proper as used throughout the specification and claims is hereby defined to include that portion of the chain link exclusive of the cover portion.

In the one-piece chain link construction of the prior art as just briefly described, several serious problems arise which it is an object of this invention to overcome.

One of the most serious problems of the prior art one-piece chain construction used in a Grate-Kiln conveyor system is that the chain bar sides of the chain link proper of the prior art one-piece construction not only operate at a high temperature at least in the portion thereof contiguous the integral cover portion but also are subjected to large temperature differentials between the portion of each respective chain bar side which is contiguous or close to the integral cover memher and the portion of the respective chain bar side which is remote from the integral cover member. This temperature differential causes a thermal stress in the chain link proper which is additive to the chain pull tensile stress to which the chain link proper is also subjected. This combined thermal stress and tensile stress are factors which weaken the prior art chain link proper and subject it to possible mechanical damage. The undesirable high operating temperature and thermal stress in the chain bar sides of the prior art chain link proper are largely due to the fact that the prior art chain link cover member is integrally attached to the chain link proper" as a unitary casting whereby the heat from the higher temperature integral cover portion is readily transferred principally by thermal conduction to the chain bar sides of the chain link proper. Due to the time factor involved in the movement of the grate conveyor through the heated zone or zones, (a relatively short period of time) and thence into a lower temperature region of atmospheric temperature, the temperature in the various portions of each chain bar side of the prior art one-piece chain link does not have time to equalize, despite the transfer of heat by thermal conduction in the one-piece chain link, thereby producing the temperature differential and resulting thermal stress just described.

In accordance with the present invention, the problem of the thermal stress in the prior art chain link proper due to the temperature differential between the portion of the chain link proper close to the integral cover and the portion of the chain link proper remote from the integral cover is solved by making the chain link in a two-piece construction in which the separate nonintegral cover member serves as a heat shield which covers the entire chain link proper and shields the chain link proper from heat radiation from the pellets carried by the conveyor. Also, by having the cover member made as a separate member which is not integral with the chain link proper, thermal conduction from the cover member to the chain link proper is significantly reduced as compared to the prior art onepiece construction. While in my new two-piece construction, heat from the pellet bed can transfer by radiation from the pellets to the nonintegral cover and by radiation from the nonintegral cover to the chain link proper, and also while heat is transferred to the chain link proper by convection gases passing through the slotted cover of the two-piece chain link assembly, the net result of the various factors described is that at a given temperature condition to which the grate conveyor may be subjected, the chain link proper of the two-piece construction of the present invention operates not only at a lower temperature but also at a more uniform temperature throughout the body thereof than the chain link proper of the one-piece chain link construction of the prior art, thereby substantially eliminating any thermal stresses in the chain link proper and permitting the chain link proper of the two-piece construction of the present invention to have greater mechanical strength and stability than the chain link proper of the one-piece chain link construction of the prior art.

Another serious problem of the prior art one-piece chain construction used in a Grate-Kiln system is that because of thermal considerations and stresses caused by the temperature differential between the higher operating temperature of the arched integral cover portion and the lower operating temperature of the remaining structure or chain link proper of the chain link of the prior art one-piece construction, it is impractical to provide a substantial number of gas passage slots in the integral arched chain link cover member of the prior art one-piece construction since the temperature differential between the chain link proper and the integral arched chain link cover member would cause a buckling of the one-piece chain unit if such plurality of slots were provided in the integral arched cover member.

For the reason just given, to the best of my knowledge it has not been known to provide cover members in the one-piece chain link construction of the prior art having more than a minimum number of slots therein (such as one slot, for example). As a result of the lack of a substantial number of slots in the integral cover portion of the prior art one-piece construction, the pellet load or other load material being carried through the heat treatment zone or zones by the grate conveyor has been improperly treated in the regions where the pellet load or the like overlies the substantially unslotted one-piece chain link of the prior art, since the unslotted construction just referred to substantially inhibits or prevents the passage of hot gases through the chain link cover, with the result that the pellet load overlying the prior art chain link cover is untreated and turns into dust. Thus, in substance, it might be said that in using the integral substantially unslotted cover members of the prior art chain link construction that each chain strand is a potential ribbon of dust." In contrast to the prior art one-piece chain link, the two-piece chain link of the present invention permits the use of a substantial number of gas passage slots or apertures in the cover member, thereby permitting better heat treatment of the material overlying the chain strand, such as a bed of mineral ore pellets.

Another problem inherent in the one-piece chain link construction of the prior art is the fact that since the cover member is formed integrally with the chain link proper, it is subject to the mechanical pulling tensions applied to the chain during the normal movement of the grate conveyor. The chain link cover member operates at a substantially higher temperature than most of the chain link proper. Since the integral arched cover member of the prior art chain link is subjected to the chain pull tensile stress and is operating at an elevated temperature, the combination of these factors frequently contributes to the mechanical failure of the prior art one-piece chain link when the yield stress of the material of which the one piece chain link is made is exceeded at a given temperature of the material and tensile stress thereon.

An important feature of the two-piece chain link construction of the present invention is that the nonintegral cover member of the two-piece construction is not subject to the tensile stresses of the mechanical tension of the pull on the chain, and hence can operate at a high temperature without danger of mechanical failure. In the two-piece construction of the present invention, the mechanical tension of the pull on the chain is carried by the chain link proper" and, due to the heat shield" effect provided in my new construction by the nonintegral cover member relative to the chain link proper," mentioned previously, the chain link proper of the new construction operates at a lower and more uniform temperature for a given operating condition than does the chain link proper of the prior art onepiece construction. Thus, both the cover member and the chain link proper of the present invention are less subject to mechanical failure than the cover member and the chain link proper of the prior art construction.

STATEMENT OF THE INVENTION Accordingly, it is an object of the present invention to provide a two-piece chain link assembly for a grate conveyor or the like used in heat treatment processes which overcomes problems associated with the onepiece chain link member of the prior art.

It is a further object of the invention to provide a twopiece chain link assembly for use with a grate conveyor or the like in which the chain link cover member is formed separately from the chain link proper of the chain link assembly, whereby to improve the mechanical strength of the chain link assembly.

It is a still further object of the invention to provide a two-piece chain link assembly for a grate conveyor or the like in which the nonintegral cover portion of the chain member serves principally as a load support, heat shield for the chain link proper, and gas passage grid, and is not required to serve as a strength member subjected to chain pull tensile stresses.

It is a still further object of the invention to provide a two-piece chain link assembly for a grate conveyor or the like in which the nonintegral cover portion of the chain link serves as a heat shield for the chain link proper, whereby to greatly reduce thermal stresses in the chain link proper with resulting greater mechanical strength in the chain link proper.

It is still another object of the invention to provide a two-piece chain link assembly including a chain link proper which serves as a strength member to which the tensile force of the pull on the chain is applied, and a cover member in overlying relation to the chain line proper, the cover member serving as a load support for material being conveyed, as a heat shield for the chain link proper, and as a gas passage grid.

It is still another object of the invention to provide in a grate conveyor, a two-piece chain link assembly including a nonintegral cover member having a substantial number of gas passage slots or apertures therein to define a gas passage grid whereby to provide improved heat treatment of material being carried by the conveyor such as ore pellets or the like.

In achievement of these objectives, there is provided in accordance with an embodiment of this invention, a two-piece chain link assembly and a chain for a grate conveyor or the like formed of a plurality of such twopiece chain link assemblies connected together. Each two-piece chain link assembly comprises a chain link proper which includes a yoke at one end and a neck at the opposite end, the neck of one chain link proper being received by and pivotally connected to the yoke of a contiguous chain link proper. A nonintegral separate cover member having gas passage slots or apertures therein is provided in overlying and contacting relation to each chain link proper, each cover member including at one end thereof projecting lips which are pivotally connected to a pivotal support carried by the conveyor, such as a pipe spacer lying on the same transverse axis of the grate conveyor as the pivotal axis of the connection between the corresponding chain link proper and a contiguous chain link proper. The other end of each cover member includes a tail portion having a part thereof which underlies an end of the cover member of a contiguous chain link assembly.

Further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a grate conveyor includ ing the two-piece chain construction of the invention;

FIG. 2 is a view in transverse section along line "-11 of FIG. 1;

FIG. 3 is a view in longitudinal section taken along line III-III of FIG. 1 showing details of one of the grates which are moved by the conveyor chains of the invention;

FIG. 4 is a top plan view of one chain link proper;

FIG. 5 is a view in side elevation of the chain link proper of FIG. 4;

FIG. 6 is a view in transverse cross-section along line VlVl of FIG. 4';

FIG. 7 is an exploded isometric view showing two chain link proper units connected in pivotal relation to each other, and also including a chain link cover adapted to cover one chain link proper unit;

FIG. 8 is a top plan view of the cover member of one chain link assembly;

FIG. 9 is a bottom plan view of the covermember of FIG. 8',

FIG. 10 is a view in transverse cross-section along line XX of FIG. llll showing the cover member assembled with respect to an underlying chain link proper; and

FIG. III is a view in side elevation of the assembly of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIG. I, there is shown a grate conveyor generally indicated at III which moves in the direction shown by the arrow in FIG. 1 and which includes a plurality of grate members such as 12A, 12B, 12C, 12A, 12B, 12C, inclusive. It will be understood that only a portion of the total conveyor length and width is shown in the view of FIG. 1. Th grates shown in the view of FIG. I are arranged in transverse rows such as the row including grates 12A, 12B and 12C; and another row including grates 12A, 12B and 12C, etc. Each transverse row of grates is connected between a pair of chain strands generally indicated at 14A and 14B, respectively. Each of the chain strands 14A and 14B is formed of a plurality of connected two-piece chain links or chain link assemblies generally indicated at 16 which form the subject matter of this invention.

The grate conveyor 10 has particular utility for conveying material being processed, such as mineral ore in the form of pellets or compacts, through a drying zone or zones and a preheating zone or zones before discharging the load material into a rotary kiln. In passing through the various drying and/or preheating zones, the load material on the conveyor (FIG. 2) is subjected to updraft or downdraft currents of heated gas or air which pass through the load material and through the slotted conveyor grates and, in the case of the present invention, through the slots in the cover members of the chain link assemblies, to be described hereinafter. Conveyor chain strands 14A and 14B are trained at the opposite ends of the run thereof around sprocket members or the like. Conveyor chain strands 14A and 1148 are supported intermediate the length thereof by support rollers such as those indicated at 27 mounted on shaft 29 (FIG. 2).

As best seen in the views of FIGS. 1, 2 and 3, each of the grate members or castings such as 12A, 12B, etc., made of cast iron or other suitable material, includes a head portion 18 which leads in the direction of travel of the conveyor and a main body or tail portion 20 which trails in the direction of travel of the conveyor. The grate member such as 12A also includes an intermediate leg portion 22 located intermediate the head portion 18 and the tail portion 20 of the grate 12A. The under surface of head portion 18 of the grate is formed with an arcuate bearing surface 24 which is adapted to pivotally mount the grate on a pivotal support means in the form of a pipelike support such as a pipe spacer 26 or the like. In the illustrated embodiment, a given pipe spacer 26 extends for the entire transverse width of three grates such as 12A, 12B and 12C. Pipe spacer 26 is supported at the opposite ends thereof by chain pins 49 carried by the chain members 16 of the two chain strands 14A and 14B, respectively. Pipe spacer 26 is coaxial with chain pins 49. It will be noted in the view of FIG. 3 that the main body portion or tail portion 20 of the grate 12A extends in a generally horizontal plane and rests at its trailing extremity on the head portion of the contiguous trailing grate member 12A.

The grate member such as 12A is secured in position about the pivotal support 26 by a grate clip 28 which in turn is secured to the lower end with respect to view of FIG. 3. of intermediate leg member 22 by suitable fastening means 30. The pivotal connection of the respective grates to the pivotal support 26 accommodates any necessary pivotal movement of the grates as, for example, when the conveyor moves from the upper to the lower pass thereof.

The grate members, such as 12A, per se form no part of this invention but have been described merely in order to properly orient and relate them to conveyor 10 and to the two-piece chain link assemblies forming part of conveyor 10.

Referring now to FIGS. 4, 5 and 6, there is shown one unit of what is herein referred to as the chain link proper" as distinguished from the cover member for the two-piece chain link assembly which will be described hereinafter in more detail. The chain link proper generally indicated at 36 is a casting of a suitable metal such as an alloy steel, or the like, and includes a pair of side bar members laterally spaced from each other and indicated at 38. Side bar members 38 define the yoke portion 40 of the chain link proper. The two side bar members 38 converge together to form the neck portion 42 of the chain link proper. The yoke portion 40 of the chain link proper is provided with bearing passages 44 therethrough, and similarly, the neck portion 42 of the chain link proper is provided with a bearing passage 46 therethrough. As will be seen in FIG. 7, when the chain link proper 36 and chain link proper 36 are assembled together, the neck portion 42' of the member 36' is received within the yoke portion 40 of member 36, with the bearing passage 44 of the yoke member 36 being aligned with the bearing passage 46 of the member 36' so that a chain pin 49, shown in dotted outline in FIG. 7, can be received in the aligned bearing passages of the two members 36 and 36' to provide a pivotal connection between chain link proper 36 and chain link proper 36'. Chain pin 49 lies along a substantially horizontal axis.

Referring now to FIGS. 7-ll, inclusive, the cover member for the two-piece chain construction is generally indicated at 50 and includes a main body portion 52, of a suitable metal such as low carbon steel or the like, and of greater lateral width than the lateral width of the underlying chain link proper shown in FIGS. 4-6 inclusive. As best seen in FIGS. 2 and lltl, the under surface of the cover member 50 rests on the upper surface of the underlying chain link proper 36 (as viewed in the upper or working run of the grate conveyor). (The lateral width of the chain link cover member is the leftto-right dimension in the views of FIGS. 1, 2 and 10.) Thus, as best seen in the transverse cross sectional views of FIGS. 2 and 10 of the drawings, the cover member 50 is of sufficiently greater transverse width than the transverse dimension of the underlying chain link proper 36 that the cover member projects laterally on either lateral side of the underlying chain link proper 36 with which the cover member is assembled as will be explained hereinafter. The upper surface of the chain link cover member as viewed in FIGS. 1, 2, 8, l0 and 11 has a slight convex arcuate curvature in its longitudinal dimension (lengthwise of the conveyor), the cover member reaching its maximum convexity intermediate the length of the cover member and its minimum convexity in the end regions where lip portions 58 (to be described) and tail portion 60 (to be described) are located. The main body portion 52 of the cover member is provided with a gas passage grid in the form of a plurality of relatively narrow slotted passages therethrough generally indicated at 54 which permit the passage of gases therethrough. In the embodiment illustrated in the drawings, thirteen such slotted passages 54 are provided and extend in a longitudinal direction relative to the lengthwise direction of travel of the chain. The passages 54 extend for a substantial part of the length of the main body portion 52 of the cover member 50. Slotted passages are sufficiently narrow (for example, ,4; inch in lateral width) to prevent any significant passage therethrough of the load material carried by the upper surface of cover member 50, but yet to permit substantially unrestricted passage therethrough of hot gases to the load material.

At the leading end of the chain link cover member 50 relative to the direction of travel of the conveyor chain, the cover member is centrally recessed as indicated at 56 to define two extensions or lips each indicated at 58 which in effect form extensions of main body portion 52. The body portion 52 of cover member 50 is also provided with trailing extension or tail portion 60 which is centrally located with respect to the transverse or lateral dimension of cover member 50. The lateral dimension of the tail portion 60 of cover member 50 is slightly less than the corresponding lateral dimension of the recess 56, whereby the tail portion 60 of one cover member 50 is adapted to be received in and feeely movable within limits relative to the recess 56 of the trailing cover member 50' as best seen in the views of FIGS. 1 and 11. The longitudinal dimension of tail portion 60 of the cover member is longer than the longitudinal dimension of recess 56, whereby when tail portion 60 of the one cover member 50 is received in recess 56 of the trailing cover member 50', the trailing end portion of the tail member 60 of one cover member 50 is adapted to underlie and trail the bounding edge 57 of recess 56 of the trailing cover member 50', as best seen in the view of FIG. 11, along the entire path of movement of the grate conveyor whereby to maintain any given cover member 50 in interfitted assembled but relatively movable relation to the contiguous cover member 50' throughout the entire path of movement of the grate conveyor.

As best seen in the views of FIGS. 9 and 11, the under surface of the laterally outer portion of each of the respective body projections or lips 58 is provided with a web portion or rib 63 having an arcuate bearing surface 64 which is adapted to rest in bearing relation on the peripheral surface of the pipelike support means or pipe spacer 26 laterally outwardly of the underlying chain link proper. The under surface of each of the body projections 58 is also provided with a downwardly and laterally extending (relative to the view of FIG. 1 1) leg portion 66 which is adapted to serve as a mounting means for a retainer bar 68 which includes an arcuate bearing portion 70 adapted to underlie the pipe spacer 26. A suitable fastening means 72 such as a bolt or the like secures retainer bar 68 in position relative to leg member 66. It can be seen, therefore, that when retainer bar 68 is mounted on leg 66 as shown in the view of FIG. 11, and with the arcuate bearing portion 64 of wet portion 63 of body projection or lip 58 resting on an oppositely disposed surface of the pipe spacer, that cover member 50 is pivotally supported on pipe spacer 26 by the bearing arrangement provided on the under surface of the oppositely disposed body projections 58 of a given cover member 50. The fit of the bearing portion 64 of body projection 58 and of the retainer bar 68 relative to pipe spacer 26 are such as to provide a pivotal connection which permits any necessary relative pivotal movement of chain link cover member 52 and pipe spacer 26 with respect to each other as may occur, for example, when the conveyor chain moves around an end sprocket or the like, or during the return run of the grate conveyor.

Pipe spacer 26 lies on the same axis transverse of the path of conveyor travel as do the chain pins 49 on which the neck portion of a given chain link proper is pivotally connected to the yoke portion of a contiguous chain link proper. The chain pins 49 extend into the ends of the hollow pipe spacers 26 to support the pipe spacers 26, chain pins 49 being coaxial with the respective pipe spacers 26.

Instead of pivotally mounting cover member 50 on pipe spacers 26, as just described, the cover member 50 may instead be pivotally mounted directly on the ends of chain pins 49 laterally outwardly of the chain link proper 36. Also, where a pipe spacer is not available, as at the left-hand side edge of the conveyor, as viewed in FIG. 1, an adaptor or bushing of the same outer diameter as pipe spacer 26 may be mounted on the chain pin to provide a pivotal support for cover member 50.

The arcuate bearing portion 64, the leg 66, and the retainer bar 68 beneath each projection or lip 58 of a given cover member are all so located as to lie laterally outwardly of the contiguous surface of the yoke portion of the associated or corresponding chain link proper.

Also, as can best be seen in the view of FIG. 11, the tail portion 60 of each cover member 50 is at all times during the operation of the conveyor retained in position by the underlying and trailing relation of the trailing end of tail portion 60 of one cover member 50 relative to edge 57 bounding recess 56 of the trailing cover member 50 (FIG. 11). The tail portion 60 of a given cover member 50, as best seen in the view of FIG. 11, extends in substantially a downward arc relative to the view of FIG. 11 so that the plane of the trailing end of tail portion 60 lies below the plane of the main body portion 52 of the trailing cover member 50 and also lies beneath and in trailing relation to the leading edge 57 of the main body portion 52 of the trailing cover member 50'. Thus, the trailing end of tail portion 60 of any given cover member lies below and in trailing relation to (relative to the direction of travel shown in FIG.

9 l) the leading edge 57 of the main body portion 52 of the contiguous trailing cover member 50. This relationship is made possible by the fact that, as previously explained, the tail member 60 is longer than the recess 56 of the next contiguous trailing cover member, so that this dimensional relationship makes it necessary for the tail portion 60 of a given cover member to extend in underlying relation to and in trailing relation to the leading edge 57 of the main body portion of the trailing cover member. The under surface of the trailing end portion of the trail member 60 of a given cover member 50 (as viewed in FIG. ill) bears on the neck portion 42 of the corresponding underlying chain link proper 36.

The underlying and trailing relation of the tail portion 60 of each cover member 50 with respect to the leading edge 57 of the contiguous trailing cover member 50 provides an interfitting relation between each cover member and the contiguous trailing cover member which maintains the cover members 50, 50', etc., in interfitted assembled relation to each other during the entire course of conveyor travel and yet permits relative movement of contiguous cover members 50, 50, etc., with respect to each other within limits to accommodate any necessary movement of the various chain elements which may occur during the course of travel of the conveyor as, for example, in traveling around the end sprockets of the grate conveyor, or during the return run of the conveyor.

It will be noted that the trailing end of tail portion 60 of each cover member 50 terminates in a reentrant curve indicated at 62. The reentrant curve 62 defines a retainer hook on tail portion 60 which prevents tail portion 60 of a given cover member 50 from moving out of underlying interfitted engagement with the trailing cover member 50' in the event that the pitch of the chain link assemblies increases, as might be due to wear on the chain pins or other bearing surfaces.

The description in the specification and claims of the tail portion of the cover member 50 as being in underlying relation to the contiguous cover member is with reference to the relationship of the members in the upper run of the conveyor.

The various dimensions and clearances of the parts are such as to permit each cover member 50 to sit loosely upon its corresponding chain link proper 36 with a limited amount of play of the cover member relative to its corresponding chain link proper, while at the same time maintaining the parts in assembled relation with respect to each other as previously described as shown in the drawings. By providing a loose fit of the cover member 50 relative to the corresponding chain link proper 36, heat transfer from the cover member to the chain link proper is reduced.

The two-piece grate conveyor chain link construction hereinbefore described represents an important improvement over the prior art one-piece chain link construction particularly in the following respects:

1. In the two-piece chain link construction of the present invention, the nonintegral separate cover member serves as a heat shield which shields the chain link proper from heat radiation from the pellets carried by the conveyor. In addition, the use of the separate cover member significantly reduces thermal connduction from the cover member to the chain link proper, as compared to the prior art one-piece chain link construction. As a result of these factors, for a given operating condition, the chain link proper of the two-piece construction not only operates at a lower temperature but also at a more uniform temperature throughout the body thereof than the chain link proper of the onepiece chain link construction of the prior art. The twopiece construction of the invention thereby substantially eliminates any thermal stresses in the chain link proper and permits the chain link proper of the present invention to have greater mechanical strength and stability than the chain link proper of the one-piece chain link construction of the prior art.

2. The use of the two-piece construction of the present invention permits the use of a significant number of slots or apertures in the cover member of the chain link, thereby permitting the passage of hot gases to the material being processed in a heat treatment process, with the result that material overlying the chain link is properly heat treated in the same manner as material overlying a slotted grate. In the prior art one-piece construction in which the chain link cover was substantially unslotted, the pellet load overlying the chain link cover was improperly treated and frequently turned to dust.

3. The use of the two-piece construction of the present invention permits the chain pull tensile stress to be carried only by the chain link proper, with the cover portion of the chain link serving principally as a load support, heat shield and gas passage grid. This is in contrast to the prior art one-piece chain link in which the integral high temperature cover member was subjected to chain pull tensile stress, which thereby greatly increased chances of mechanical failure of the chain link.

It will be understood that a complete transverse section of conveyor 10 may include a greater number of grate castings and a greater numbe of chain strands than shown in the drawings.

From the foregoing detailed description of the present invention, it has been shown how the objects of the invention have been obtained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A two-piece chain link assembly for use as part of a grate conveyor or the like wly'ch conveys material being heat treated, comprising a chain link proper adapted to be pivotally connected to other chain links proper, and a separate nonintegral cover member mounted in overlying relation to said chain link proper, said cover member having gas passages therethrough to define a gas passage grid for said cover member whereby material in overlying relation to said cover member may be subjected to heat treatment by heated gases flowing through said cover member, said cover member including a main body portion having a pair of lip portions extending from one end thereof and a tail portion extending from the opposite end thereof, said lip portions being spaced from each other laterally of said cover member to define a recess therebetween, said lip portions being pivotally mounted about a pivotal axis common with that of the pivotal connection of one end of the corresponding chain link proper to the chain link proper of another chain link assembly contiguous said lip portions at one end of the respective chain link assembly, support means lying along said pivotal axis for pivotally connecting said one end of said corresponding chain link proper to said chain link proper of said another chain link assembly and for pivotally mounting said lip portions of said cover member, said tail portion being received in the recess between the lip portions of the cover member of still another chain link assembly contiguous said tail portion, at the opposite end of the respective chain link assembly, said tail portion being dimensioned so as to substantially cover said recess while still permitting relative movement of the interengaged contiguous cover members, said tail portion being contoured and dimensioned to extend beyond said recess to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.

2. A two-piece chain link assembly as defined in claim 1 in which said chain link proper includes a yoke portion at one end and a neck portion at its opposite end, said yoke portion being pivotally connected to the neck portion of another chain link proper.

3. A two-piece chain link assembly as defined in claim 1 in which said tail portion curves downwardly to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.

4. A two-piece chain link assembly as defined in claim 3 in which the terminal portion of said tail portion is formed with a reentrant curve.

5. A grate conveyor for moving a material being heat treated through a path of travel, said conveyor including a plurality of grate members, a conveyor chain connected to said grate members for moving said grate members through said path of travel, said chain comprising a plurality of pivotally connected chain link assemblies, said chain link assemblies respectively comprising a chain link proper pivotally connected at each end thereof to a separate chain link proper of a corresponding contiguous chain link assembly and a separate nonintegral cover member corresponding to and positioned in overlying relation to each of the respective individual chain links proper, the respective cover members having gas passages therethrough to define a gas passage grid for each cover member whereby material in overlying relation to said cover members may be subjected to heat treatment by heated gases flowing through said cover members, each respective cover member including a main body portion having a pair of lip portions extending from one end thereof and a tail portion extending from the opposite end thereof, said lip portions being spaced from each other laterally of the respective cover member to define a recess therebetween, said lip portions being pivotally mounted about a pivotal axis which is common with that of the pivotal connection of one end of the corresponding chain link proper to the chain link proper of another chain link assembly contiguous said lip portions at one end of the respective chain link assembly, support means movable with said conveyor and lying along said pivotal axis for pivotally connecting said corresponding chain link proper to said chain link proper of said another chain link assembly and for pivotally mounting said lip portions of said cover member, said tail portion being received in the recess between the lip portions of the cover member of still another chain link assembly contiguous said tail portion at the opposite end of the respective chain link assembly, said tail portion being dimensioned so as to substantially cover said recess while still permitting relative movement of the interengaged contiguous cover members, said tail portion being contoured and dimensioned to extend lengthwise beyond said recess and to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.

6. A grate conveyor as defined in claim 5 in which the chain link proper of the respective two-piece chain link assemblies includes a yoke portion at one end and a neck portion at its opposite end, said yoke portion being pivotally connected to the neck portion of the chain link proper of a contiguous chain link assembly.

7. A grate conveyor as defined in claim 5 in which said tail portion of the cover member of the respective two-piece chain link assemblies curves downwardly to be received in underlying relation to the main body portion of the cover member of the corresponding still another chain link assembly.

8. A grate conveyor as defined in claim 7 in which the terminal portion of the tail portion of the respective cover members is formed with a reentrant curve. 

1. A two-piece chain link assembly for use as part of a grate conveyor or the like which conveys material being heat treated, comprising a chain link proper adapted to be pivotally connected to other chain links proper, and a separate nonintegral cover member mounted in overlying relation to said chain link proper, said cover member having gas passages therethrough to define a gas passage grid for said cover member whereby material in overlying relation to said cover memBer may be subjected to heat treatment by heated gases flowing through said cover member, said cover member including a main body portion having a pair of lip portions extending from one end thereof and a tail portion extending from the opposite end thereof, said lip portions being spaced from each other laterally of said cover member to define a recess therebetween, said lip portions being pivotally mounted about a pivotal axis common with that of the pivotal connection of one end of the corresponding chain link proper to the chain link proper of another chain link assembly contiguous said lip portions at one end of the respective chain link assembly, support means lying along said pivotal axis for pivotally connecting said one end of said corresponding chain link proper to said chain link proper of said another chain link assembly and for pivotally mounting said lip portions of said cover member, said tail portion being received in the recess between the lip portions of the cover member of still another chain link assembly contiguous said tail portion, at the opposite end of the respective chain link assembly, said tail portion being dimensioned so as to substantially cover said recess while still permitting relative movement of the interengaged contiguous cover members, said tail portion being contoured and dimensioned to extend beyond said recess to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.
 2. A two-piece chain link assembly as defined in claim 1 in which said chain link proper includes a yoke portion at one end and a neck portion at its opposite end, said yoke portion being pivotally connected to the neck portion of another chain link proper.
 3. A two-piece chain link assembly as defined in claim 1 in which said tail portion curves downwardly to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.
 4. A two-piece chain link assembly as defined in claim 3 in which the terminal portion of said tail portion is formed with a reentrant curve.
 5. A grate conveyor for moving a material being heat treated through a path of travel, said conveyor including a plurality of grate members, a conveyor chain connected to said grate members for moving said grate members through said path of travel, said chain comprising a plurality of pivotally connected chain link assemblies, said chain link assemblies respectively comprising a chain link proper pivotally connected at each end thereof to a separate chain link proper of a corresponding contiguous chain link assembly and a separate nonintegral cover member corresponding to and positioned in overlying relation to each of the respective individual chain links proper, the respective cover members having gas passages therethrough to define a gas passage grid for each cover member whereby material in overlying relation to said cover members may be subjected to heat treatment by heated gases flowing through said cover members, each respective cover member including a main body portion having a pair of lip portions extending from one end thereof and a tail portion extending from the opposite end thereof, said lip portions being spaced from each other laterally of the respective cover member to define a recess therebetween, said lip portions being pivotally mounted about a pivotal axis which is common with that of the pivotal connection of one end of the corresponding chain link proper to the chain link proper of another chain link assembly contiguous said lip portions at one end of the respective chain link assembly, support means movable with said conveyor and lying along said pivotal axis for pivotally connecting said corresponding chain link proper to said chain link proper of said another chain link assembly and for pivotally mounting said lip portions of said cover member, said tail portion being received in the recess between the lip portions of the cover member of still another chain lInk assembly contiguous said tail portion at the opposite end of the respective chain link assembly, said tail portion being dimensioned so as to substantially cover said recess while still permitting relative movement of the interengaged contiguous cover members, said tail portion being contoured and dimensioned to extend lengthwise beyond said recess and to be received in underlying relation to the main body portion of the cover member of said still another chain link assembly.
 6. A grate conveyor as defined in claim 5 in which the chain link proper of the respective two-piece chain link assemblies includes a yoke portion at one end and a neck portion at its opposite end, said yoke portion being pivotally connected to the neck portion of the chain link proper of a contiguous chain link assembly.
 7. A grate conveyor as defined in claim 5 in which said tail portion of the cover member of the respective two-piece chain link assemblies curves downwardly to be received in underlying relation to the main body portion of the cover member of the corresponding still another chain link assembly.
 8. A grate conveyor as defined in claim 7 in which the terminal portion of the tail portion of the respective cover members is formed with a reentrant curve. 